Technical Field
The inventions relate to optical isolators and optical circulators, methods of using optical isolators and optical circulators, and apparatus including optical isolators and optical circulators.
Related Art
This section introduces aspects that may be help to facilitate a better understanding of the inventions. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.
An optical isolator is an optical component having two optical ports, which allows light to pass through the two optical ports in one direction and blocks light from passing through the two optical ports in the opposite direction. In particular, an optical isolator provides a much higher attenuation for light passing through the two optical ports in one direction than for light passing through the two optical ports in the opposite direction.
Optical isolators are believed to not satisfy Lorentz reciprocity. Some optical isolators do not satisfy Lorentz reciprocity due to the incorporation of magneto-optical material(s) therein. Magneto-optical materials typically break Lorentz reciprocity due to the presence of an asymmetric magnetic permeability.
Optical isolators have important uses in contemporary optical systems. For example, an optical isolator may be used to protect a laser or an optical amplifier from optical feedback. In the absence of an optical isolator, such optical feedback may occur due to external light received at the optical output of the laser or optical amplifier. As an example, the receipt of external light in a laser having distributed optical feedback may destabilize the output optical wavelength of the laser. The addition of an optical isolator to the optical output of the laser can remove or attenuate such unwanted optical feedback.